Electromagnetic switch



Dec. 10, 1940. WELLS ETAL 2,224,417

ELEGTROMAGNET I C SWITCH Original Filed July 3, 1936 6 Sheets-Sheet l Srwentors 509M9 5 wally and THEIR (Ittorneg Dec. 10, 1940. w. B. WELLS ET AL ELECTROMAGNETIC SWITCH Original Filed July 3, 1956 6 Sheets-$heet 2 ooliizam.

THEIR (Ittorneg Dec, 10, 1940. w. B. WELLS ETAL ELECTROMAGNETIC SWITCH Original Filed July 3, 1956 6 Sheets-Sheet 4 Zmventor t d m n m ah m m m e w m B H gm T m may ww Dec. 10, 1940. w. B. WELLS ETAL ELECTROMAGNETIC SWITCH 6 Sheets-Sheet 5 Original Filed July 5, 1956 Z'mnentors ZUQJZQgBll/QZZJ and LUilliamH 0012220305.

THEIR (Ittorneg ELECTROMAGNETIC SWITCH Original Filed July 3, 1936 6 Sheets-Sheet 6 Snoentors werleg BlUellJ and THEIR attorney Patented Dec. 10, 1940 UNITED STATES PATENT OFFICE ELECTROMAGNETIC SWITCH sylvania Original application July 3, 1936, Serial No. 88,768, now Patent No. 2,172,724, dated September 12, 1939. Divided and this application March 23, 1937, Serial No. 132,520 1 10 Claims.

Our invention relates to an electromagnetic switch for use in connection with light signals.

The present application is a division of our copending application, Serial No. 88,768, filed on July 3, 1936, for Light signals which became Patent No. 2,172,724 on Sept. 12, 1939.

We shall describe one form of light signals embodying our invention, and shall then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a top plan view showing one form of light signal embodying our invention. Fig. 2 is a front view of the signal illustrated in Fig. 1 with the glass cover which encloses the operating mechanism and certain of the other parts shown in section to better illustrate the construction of the operating mechanism. Fig. 3 is a view partly in section and partly in elevation of the signal shown in Figs. 1 and 2. Fig. 4 is a rear elevational view with the cover removed of the signal shown in the preceding views. Fig. 5 is an isometric view of the field structure forming part of the operating mechanism for the signal in the preceding views, certain of the parts being broken away to better illustrate the construction. Fig. 6 is an isometric view of the rotor forming part of the mechanism for the signal illustrated in Figs. 1 to 4, inclusive. Fig. 7 is a detail view, showing on an enlarged scale, a portion of the operating mechanism for the signal illustrated in Figs. 1 to 4, inclusive. Fig. 8 is a detail sectional view taken on the line VIIIVIII of Fig. 1. Fig. 9 is a diagrammatic view showing operating circuits for the mechanism. Fig. 10 is a detail view showing a modification of a portion of the mechanism shown in Figs. 2, 3, and 4.

Similar reference characters refer to similar parts in each of the several views.

Referring first to Figs. 1 to 4, inclusive, the signal comprises a suitable top plate A of insulating material, which top plate serves as a support for the operating and contact mechanisms of the signal. Formed in the top plate A adjacent the right-hand end thereof as viewed in Fig. 3 is a transversely extending rectangular slot l, and secured to the upper side of the top plate in vertical alignment with this slot, by means of machine screws 2 and 3 is a casing B, which casing, in the form here shown, is substantially semi-cylindrical in shape. The screws 2 each extend upwardly through clearance holes in the top late and are screwed into tapped inserts which are molded in a flange 5 that is formed on the bottom of the casing B, while the screws 3 each extend downwardly through clearance holes (Cl. 2ii0104) in the flange 5 and are screwed into threaded holes 21 formed in the backstrap 2| which comprises a part of the operating mechanism of the relay, as will appear more fully hereinafter. The front and rear walls of the casing B are pro- 'vided with aligned circular openings 6 and l and secured to this casing adjacent the cute;- sides of these openings by means of machine screws 8 are ring members 9 which carry aligned circular-windows ID of transparent glass. The ring members 9 are similar, and are preferably constructed of pressed steel to decrease their cost of manufacture. The screws 8 which fasten the ring members to the casing pass through clearance holes in the ring members, and are screwed into tapped inserts which are molded in the casing. The rear side of the casing, that isto say, the left-hand side as viewed in Fig. 3 is provided with triangular strengthening ribs II, as will readily be seen by an inspection of the drawings. 7

Extending upwardly into the casing B through the slot I is a. spectacle arm l2 which is provided at its upper end with three differently colored filters'l3, l4, and i5, as best seen in Figs.

2 and 4. This arm is secured at its lower end to the operating mechanism of the signal in a i "ii manner which will appear hereinafter, and is capable of assuming acentral or vertical position in which the filter I4 is located in axial alignment with the windows It, a right-hand position, as viewed in Fig. 4 in which the filter I3 is located in axial alignment with the windows Ill, and a left-hand position, as viewed in Fig. 4 in which the filter I5 is located in axial alignment with the Windows H). In utilizing the signal, the light rays from a suitable optical assembly forming no part of our present invention are caused to pass through the windows, and to converge at a focal point at or near the center of the filterwhich is then in axial alignment with the windows Ill, and it will be apparent, therefore, that the light rays passing through the focal point will pass through one or the other of the filters, so that only rays of the color which are not filtered out can emerge from the signal. Since the filters are differently colored, it follows that the signal is capable of displaying three different aspects depending upon which of the filters is located in axial alignment with the windows III. In the practical application of our signal to railway signaling, the spectacle arm i2 is biased to the vertical position and the filter i4 is colored red, so that when the arm occupies its vertical position, the projected beam is red, indicating stop. The filter I is colored green so that when the arm l2 occupies its lefthand position, the beam emitted by the signal is green, indicating proceed. The filter I3 is colored yellow so that when the arm I2 occupies its right-hand position, the beam emitted by the signal is yellow, indicating caution.

The operating mechanism for the signal is essentially the same as that described in the copending application for Letters Patent of the United States, Serial No. 84,501, filed on June 10, 1936, by Wesley B. Wells, one of the co-inventors of the present invention, for Light signals, which application became Patent No. 2,133,603 on 00- tober 18, 1938. Briefly described, this mechanism comprises a field structure F which is best illustrated in Fig. 5, and a rotor R which is best illustrated in Fig. 6. Referring to Fig. 5, the field structure comprises two spaced magnets M and M each consisting of a plurality of permanently magnetized rectangular bars 20, the like poles of which are connected by magnetizable spaced parallel backstraps 2| and 22, respectively. The method of connecting the magnets with the backstraps, and the method of securing the backstraps together is fully described in the previously referred to Wells application, and need not, therefore, be repeated herein. Associated with the backstraps are four L--shaped pole pieces 23, 24, 25, and 26, two of which, 23 and 24, are secured to the upper backstrap 2|, and the remaining two of which, 25 and 26, are secured to the lower backstrap 22. The pole pieces 23 and 24 are spacedv apart, and are disposed with their vertical legs extending downwardly on opposite sides of the backstrap 2|, and the polepieces 25 and 28 are similarly spaced apart and are disposed with their vertical legs extending upwardly on opposite sides of the backstrap 22 directly opposite the downwardly extending legs of the pole pieces 23 and 24. It will be seen, therefore, that the field structure comprises four pole pieces, two of which, 23 and 25, are located on one side of and adjacent the opposite ends of the backstraps 2| and 22, and the other two of which, 24 and 25, are located on the other side of and adjacent the opposite ends of the backstraps 2| and 22. It will also be apparent that the pole pieces 23 and 24 will be of one polarity, whilethe pole pieces 25 and 26 will be of the opposite polarity. For example, if thebars 20 are disposed withtheir north magnetic .poles located at the upper ends of the bars, the pole pieces 23 and 24 will be north poles, and the pole pieces 25 and 26 will be south poles. The outer faces of the vertically extending legs of each pair of pole pieces are disposed in the same vertical plane.

The field structure F is suspended from the top plate A by means of the previously described screws 3, the lower ends of which are screwed into threaded holes 21 provided in the upper backstrap 2| adjacent the opposite ends thereof, as shown in Fig. 2. The field structure is also suspended from the topplate by means of a screw 28 which extends downwardly. through a clearance hole, in the top plate, and is screwed into a threaded hole formed in a supporting strap 29 which is bolted to the upper side of the backstrap 2| near the center thereof as best seen in Fig. 3. It willbe seen, therefore, that the field structure is securely held in place against the underside of the top plate.

Attached to the lower backstrap 22 between the pole pieces 25 and 26 by means of screws 33 I seen in Fig. 3.

is a non-magnetizable bracket 3|. This bracket is substantially U-shaped, and the upwardly extending arms 3| and 3| thereof areprovided in their upper ends with aligned knife-edge bearings 32 and 33, respectively, in which the rotor R referred to hereinbefore is journalled, as best The bearings 32 and '33 may be of any suitable construction, but as here shown, these bearings are similar in all respects to those described and claimed in a copending application for Letters Patent of the United States, Serial No. 748,506, filed on October 16, 1934, by W. B. Wells, for Bearings and method of manufacturing the same, which application became Patent No. 2,069,908 on Feb. 9, 1937.

Referring now also to Fig. 6, the rotor R, in

the form here shown, comprises a core 35 of suitable magnetizable material, such as silicon steel, provided adjacent its ends with shoulders against which downwardly extending armatures 35 and 31 are clamped by means of nuts 38 and 39', respectively. End pins 40 of suitable material, such as hardened steel, are inserted in the ends of the core 35, and these end pins are mounted to rotate in the knife-edge bearings previously described. The armature 36 is adapted to cooperate with the pole pieces 24 and 25, and is spaced from the outer faces of the vertical legs of these pole pieces, by vertical air gaps, as will be seen from an inspection of Fig. 3. is likewise adapted to cooperatewith the pole pieces 23 and 26, and is spaced from the outer The armature 31 faces of the vertical legs of these pole pieces by vertical air gaps. The armatures and 31 are of magnetizable material, and are provided with ears 36 36 37 and 31 which ears taper from the center of the armatures as shown for reasons which will be explained hereinafter.

Clamped between the armature 3G and the nut 38 is a triangular plate 4|, and attached to the outer side of this plate on opposite sides of the core 35 of the rotor R, as best seen in Figs. 3, 4, and 6, are two studs 42 and 42*, which carry rollers 43 and 43 respectively. A supporting bracket 44 is removably secured to the arm 3| of the U-shaped bracket 3| by means of machine screws 45, and pivotally supported at one end on pivot pins 45 and 46* mounted in bifurcated ears 4'! and 41 respectively, which are provided on the bracket 44, are two operating arms 48 and 48, the free ends of which extend toward, and cooperate with, the rollers 43 and 43*, respectively. A counterweight arm 49 is pivotally supported intermediate its ends on the operating arm 48 by means of a pivot pin 5|] mounted in pin supports 5 l secured to the operating arm, and a counterweight arm 49 is similarly pivotally supported intermediate its ends on the operating arm 48 by means. of a pivot pin 50 mounted in pin supports 5| secured to this latter operating arm. The counterweight arm 49 carries a counterweight 52 which constantly biases this counterweight arm to a position in which end thereof engages the upper side of the operating arm 48*, and the counterweight 52 and counterweight arm 49 together bias the operating arm 48' to a position in which a downwardly extending projection 5'! which is formed on the operating arm engages the inner end of an adjustable stop screw 53* that is screwed through the lower portion of the ear 41 of the supporting bracket 44. The stop screws 53 and 53 are provided with lock nuts 58 and 58 for locking the stop screws in their adjusted positions. The outer end of the operating arm 48 is provided with an upstanding lug 54 which cooperates with the outer end of the counterweight arm 49 to limit the amount of rotation of the counterweight arm 49 relative to the operating arm 48*, and the outer end of the operating arm 48 is similarly provided with an upstanding lug 54 which cooperates with the outer end of the counterweight arm 49 to limit the rotation of this counterweight arm relative to the operating arm 48 The counterweight 52 is slotted in its underside at 55 (see Fig. '7) to receive the counterweight arm, and is adapted to be fastened in an adjusted longitudinal position on the arm by means of a set screw 56 which is screwed through the weight at one side of the slot for engagement with the arm. The set screw 56 carries a lock nut 59 by means of which the set screw is prevented from becoming unscrewed. The counterweight 52 is similar in construction to the counterweight 52 and is secured to the associated counterweight arm 49 in the same manner that the counterweight 52 is secured to the counterweight arm 49*. The operating arms 48 and 48 normally both rest on the associated rollers 431 and 43 and the stop screws 53 and 53 are so adjusted that when the operating arms are both engaging the associated rollers, and the downwardly extending projections 51 and 51' are each engaging the associated stop screws 53 and 53", the rotor R will occupy its proper normal position. It will be seen, therefore, that if the rotor R is rotated from its normal position in a clockwise direction, as viewed in Fig. 4, the operating arm 8- will be raised, but that, if the rotor is rotated from its normal position in the opposite or counter-clockwise direction, the operating arm 48 will then be raised, thereby providing means whereby the rotor is biased to a middle or normal position in which the longer axes of the armatures 36 and 31 are substantially vertical. It will also be seen that the weight of the operating arms 48* and 48 assists in biasing the rotor to its normal position. The reasons for providing the auxiliary counterweight arms 49 and 49 and for loosely pivoting these counterweight arms on the operating arms in the manner described, will be made clear hereinafter.

It should be pointed out that the pivot p ns 46* and 46 about which the operating arms 48 and 48 rotate are located in such positions with resheet to the points at which the rollers 43 and 43 engage the operating arms, and the parts are so proportioned, that when an arm is being lifted by a roller, the point of contact between the arm and the roller will move outwardly along the arm, and around the roller in a counter-clockwise direction for the roller 43, and in a clockwise direction for the roller 43, so that there is substantially no sliding motion between the rollers and the arms.

The operating arms-48 and 48 in addition to serving as a part of the means for biasing the rotor R to its normal position, are arranged to operate separate contact mechanisms. These contact mechanisms are similar, and their corresponding parts are designated by the same reference characters with the distinguishing exponents a and b, respectively so that an understanding of both will be had from a description of only one. Referring particularly to the contact mechanism controlled by the operating arm 48, for example, this contact mechanism comprises a plurality of flexible contact fingers 60, fil and 62 secured by means of an insulating support 63 to a depending leg 64 forming part of a rocker 65 The rocker 65 is pivotally supported on horizontally aligned trunnion screws 66 mounted in upstanding arms 61 formed on one end of the bracket 44, and is provided with a laterally extending arm 68 which projects toward the operating arm 48 The free end 69 of the arm 68 is bent at right angles to the a position that the arm 68 is constantly held in engagement with the pin 10, and it will be seen, therefore, that the rocker 65 assists in biasing the rotor to its normal position. It will also be seen that when the rotor is rotated away from its normal position in a clockwise direction, as viewed in Fig. 4, the resultant rotation of the operating arm 48 will act through the pin 10 and arm 68 to rotate the rocker in opposition to its bias. The extreme position to which the rocker is free to rotate in opposition to its bias is limited by an adjustable stop screw H which is screwed through 21. depending lug l2 formed on the underside of the bracket 44, and which screw cooperates with the lower end of the depending leg 6A, and it follows that by adjusting the stop screw H the extreme position to which the rotor is free to rotate in a clockwise direction, as viewed in Fig. 4, may be limited. Mounted on the stop screw H is a lock nut 13 which serves to lock the stop screw in an adjusted position. For convenience in describing the remainder of the signal, we shall hereinafter refer to the position which the rocker occupies when the rotor occupies its normal position as the normal position of the rocker, and the position which the rocker occupies when the leg 64 is engaging the stop screw H as the operated position of the rocker. When the rocker occupies its normal position, the contact fingers (ill and 62 engage fixed contact .members 14' and H3 secured to terminal posts H and 19 mounted on the top plate A, to close back contacts 60 -14 and 62 18 When, however, the rocker is rotated to its operated position, the contact fingers 60 and 62 then move out of engagement with the fixed contact members 14 and 16 to open the contacts 6ll*"-|4 and 62 16 and the contact finger 6| moves into engagement with a fixed contact member I5 secured to a terminal post I8 mounted on top plate A, to close a front contact lilT5 To facilitate making electrical connections with the contact fingers 60 fil and 62", these contact fingers are connected by means of flexible connectors 80, 8M, and 8'2 with terminal posts 83, 84. and 85*, respectively, mounted on the top plate A.

The lower end of the previously described spectacle arm. I2 is in the form of a fiat punching, and is secured to the armature 31 of the rotor R in such manner that when the rotor occupies its normal position, the filter l4 carried by the spectools arm will be in :axial alignment with the windows I0. The parts are so adjusted and so proportioned that if the rotor is rotated in the clockwise-direction, as viewed in Fig. 4, to the position in which the leg 64 of the rocker 65* isen'gagingthe stop screw 1 I the filter I3 will then be in axial alignment'with the windows I0, and that, if the rotor is rotated in a counterclockwise -direction, as viewed in Fig. 4, to the position in which the leg 64 of the rocker 65 is engaging the :stop screw H the filter I5 will then be located in axial alignment with the windows (I0.

Surrounding the core 35 of rotor R is a rotor coil 86 which, in the -form here shown, comprises the usual helix of insulating wire wound by means of an automatic machine on a tube of insulation 81, which surrounds a heavy sleeve 88 of suitable conducting material, such as copper, between insulating end plates 89 and 90 that are held in place on the sleeve by spinning over the ends ofthe sleeve. In constructing the coil 86, the insulation is placed on the copper sleeve before the winding is applied, and after the winding .hasbeen applied, the end plates are then slipped .over the protruding ends of the copper sleeveand are then fastened in place. It will be .noted that the tube of insulation extends beyond the winding and fits into annular recesses formed in the insulating end plates, which construction greatly increases the insulation break-down volt- .age between the winding and the copper sleeve. The coil is supported between the backstraps 2! and 22 by means of two brackets 9I which are fastened, as by riveting, to the backstra'p. The brackets 9.I extend longitudinally at the top and bottom of the coil, and fit'into suitable slots 92 formed in the end plates .39 and 99. The ends of the brackets 9| are bent over to form lugs 9W which engage the end plates to hold the coil in the proper longitudinal position with respect to .the core. The leads 86 and 86- of the coil 86 are secured to terminal posts 93 and 94 mounted onv the top plate A, as shown in Fig. .8. The lower ends .of the terminal posts-93 and 94 are shunted by a earborundum lightning arrester 9-5 of standard construction. I

It is desirable that the clearance between the core 35 and the coil 86should be as small as possible, but since the core 35 is mounted to rotate within the coil, it is essential that the core and coil do not touch each other. It will be apparent, therefore, that the core 35 should be accurately centered with respect to the coil 86. facilitate this centering, we preferably construct the brackets 9! of suitable material such as brass, which may be bent sufiiciently to permit the necessary vertical adjustment of the coil, and'we so proportion the brackets that, after they have been bent, they will not permit motion of the coil due to vibration or jarring of the signal. Furthermore, we construct the holes in the brackets 3| through which the screws 30, which fasten this bracket to the backstrap 22, pass, with sufficient clearance so that this backstrap, and hence the core .35 of the rotor :R. carried thereby, may be moved at right angles to the axis of the coil in the horizontal plane. It follows that with adjustments between the core and coil in both planes, the core can be conveniently and accurately centered with respectto the coil.

The rotor coil 85 is intended to be reversibly supplied with current, and for this purpose we have shown in Fig. 9 a battery 96 which is connected with this coil over a pole changer P. As

here shown, the pole changer P is manually operated, but in actualpractice this pole changer will usually be replaced by pole-changing contacts of a relay, or by the contacts of other signals which are similar to the signals here shown.

In addition to the terminal posts previously referred to, the top plate A also carries two additional terminal posts 9'! and 98 which serve as connections for the lamp of the optical unit which cooperates with the signal mechanism.

The signal as a whole is intended to be mountedwithin an outer housing which contains means for projecting a light beam through the windows I0 and the aligned filter, and to facilitate securing the signal within this housing, a transversely extending strap 99 is secured to the upper side of the top plate A by means of screws I00 which extend downwardly through clearance holes in the strap 99, and are screwedinto threaded inserts molded in the top plate. The strap 99 .is provided adjacent each end with upstanding .apertured lugs IOI for the reception of supporting bolts, and the top plate A is provided in its forward end with a tubular insert I02 for the reception of a projecting pin which is provided in the outer housing.

The strap 99 is also provided with holes for the reception -of,the lower ends of an inverted U-shaped bolt I03 which bolt serves as a handle to facilitate carrying the signal and mounting it in the outer housing.

The operating mechanism is enclosed within a glass cover I04 hcldin place by means of a U- shaped strap I05. This strap surrounds thecover near the center thereof, and .is provided at its upper ends with inwardly extending ears I06 which project into recesses I07 formed in the opposite sides of the top plate .A. The ears I00 are each provided with a hole I08 which aligns with a hole I09 provided in the supporting strap 99, and have secured to their undersides as by riveting strengthening plates H0 provided with threadedholes H I which align with the holes I08 and I09. A screw H 2 extends downwardly through each pair of aligned .holes I09 and I08 and is screwed at its lower end into the associated threaded hole III. The parts are so proportioned that when thescrews I I-2 are tightened, the strap I05 and screws assist in fastening the strap 99 to the .top plate A. The strap I05 assists in supporting the weight of the signal when the signal is supported by means of lugs I0| or the handle I03.

Assuming for purposes of explanation that the magnets M and M are so disposed that the pole pieces 23 and 24 become north poles and the pole pieces 25 and 26 become south poles, the operation of the relay as a whole is as follows: When pole changer P occupies its middle position in which no current is supplied to coil 86, as showninthedrawings,the only flux which threads the armatures 30 and 3i is the flux from the associated pole pieces 24, 2B, and 23, .25, and the armatures are so shaped, and the parts are so proportioned that this flux will exert no appreciable torque on the rotor. The rotor is therefore held in its normal position by the biasing means described hereinbefore. When the rotor occupies this position, the filter I 4 is located in axial alignment with the windows I0, and the beam projected by the signal will therefore be red. Furthermore, the back contacts SO -14 62l-6 Gil -14 and 62 -'I9 are then closed, while the contacts M -45 and 6-I 'IEi are both open.

armature 31 becomes a north pole.

If, now, pole changer P is thrown in such a direction that winding 86 is supplied with current of normal polarity, armature 36 becomes a north pole and armature 31 becomes a south pole. Un-

der these conditions, the pole piece 24, being a north pole, repels the armature 36, and the pole piece 25, being a south pole, attracts the armature 36; while the pole piece 23, being a north pole, attracts the armature 31, and the pole piece 26, being a south pole, repels the armature 31. A torque is therefore exerted on rotor R which rotates the rotor in a counter-clockwise direction, as viewed in Fig. 4. This rotation of the rotor raises the operating arm 48' to its upper position and rotates the rocker 65 to its operated position, thereby opening the contacts Go -14 and 62"-'16 and closing the contact BI -15 This rotation of the rotor also brings the filter I5 into axial alignment with the windows [0, so that the beam projected by the signal will then be colored green. The counter-clockwise rotation of the rotor, however, does not affect the operating arm 48, so that contacts Bil -14 and M -16 remain closed and front contact 6 I -15 remains open. The rotor will now remain in the position in which the filter I5 is located in axial alignment with the windows l until pole changer P is operated to deenergize coil 86, at which time the rotor will be returned to its normal position by the biasing means associated with the operating arm 43 If pole changer P is thrown in such a direction that coil 86 is supplied with current of reverse polarity, armature 36 becomes a south pole and Under these conditions, armature 36 is attracted by pole piece 24 and repelled by pole piece 25, while armature 31 is repelled by pole piece 23 and is attracted by pole piece 26, so that a torque is exerted on rotor R which rotates the rotor in a clockwise direction as viewed in Fig. 4. This rotation raises operating arm 48 to its upper position, thereby operating rocker 65*- to open contacts 6iI"= --14 and 62 -16 and to close contact 6I 15. This rotation also brings filter l3 into axial alignment with the windows 10, so that the beam projected by the signal will then be yellow. During this rotation, operating arm 48 remains in the position shown, so that back contacts BB -14 and l32 1ii remain closed, and front contact (M --15 remains open. When pole changer P is operated to deenergize coil 86, the armature will then return to its normal position due to the biasing means associated with the operating It should be particularly pointed out that since the coil66 is slow acting, the flux-which is set up in the rotor B when this coil is energized builds up slowly, and the magnetic torque exerted on the rotor due to this flux, increases slowly,

so that the rotor moves slowly from its normal position to either of its operated positions. This slow operation of the rotor minimizes the momentum acquired by the rotor, and hence, reduces 1 the tendency of the rotor to rebound when the "Furthermore, due to the fact that the armatures 36 and 31 are mounted in depending vertical positions in the manner shown, the use of counterrotor to be reduced, thereby further minimizing the tendency of the rotor to rebound. In addition, the counterweight assembly previously described permits each counterweight and counterweight arm to overtravel until the arm strikes the associated stop 54 on the operating arm, thus still further reducing the tendency of the rotor to rebound. It should also be noted that since the coil 86 is slow acting, the decay of the flux in the rotor upon the deenergization of the coil is also retarded, thereby causing the magnetic torque exerted on the rotor by this flux to decrease slowly, with the result that the rotor returns slowly to its normal position. By slowing up the motion of the rotor while returning to its normal position in this manner, the tendency of the armatures to overtravel and rock the rotor in its normal position due to the momentum acquired by the rotating parts is almost entirely eliminated. It will also be apparent that the use of the slow-acting coil also retards the decay and build-up of the magnetic flux of the rotor when the polarity of the current supplied to the coil 86 is reversed, thus slowing up the motion of the rotor when going from one operated position to the other and hence reducing the tendency of the rotor to rebound under these conditions.

i It should be pointed out, further, that since the armatures 36 and 31 are formed with tapered ears as previously described, a greater torque is exerted on the rotor near the end of its stroke in either direction than at the beginning, this added torque being desirable for compressing the front contacts of the signal.

If desired the counterweight arms 49 and 49 may be eliminated and the counterweights mounted directly on the operating arms 48 and 48 as shown in connection with the operating arm 48 in Fig. 10. The operation of the signal when constructed in this manner is essentially the same as that previously described.

One advantage of a signal embodying our invention is that since all parts are mounted on an insulating top plate, the possibility of lightning jumping from the coil 86 to the rotor and field structure, and hence to ground through the signal housing and supporting mast is greatly reduced. Furthermore, the particular construction of the operating coil 86 further reduces this possibility as pointed out hereinbefore.

Another advantage of a signal embodying our invention is that since the operating unit does not carry the light unit and lens assembly, the manufacture and handling of the signal is greatly simplified. Furthermore, the operating temperature of the operating mechanism is greatly reduced.

Another advantage of a signal embodying our invention is that the rotor is biased to return to its normal position even if the contact carrying rockers should stick in either of their operated positions, thus insuring that the signal will display the proper color indication independently of the position of the contacts of the contact mechanism.

A further advantage of a signal embodying our invention is that since the contact fingers are mounted in substantially vertical positions the tendency of dirt to remain'on the contact surfaces is greatly decreased.

A further advantage of a signal embodying our invention is that it provides more contacts than has heretofore been provided, andgreatly facilitates inspection of the contacts.

A. further advantage of asignaI embodying. our invention is that the various stop screws, for limitingthe; movement of. therotor and contact mechchanges and modifications, may be made therein within the scope. of the. appended claims without departing; from the spirit, and scope of our invention. I I

Having thus described our invention, what we claim is:

1. A mechanism comprising a rotor movable between an. intermediate and two extreme positions, means for moving; said rotor fromits intermediate position to either extreme position, two

rollers secured to said rotor on opposite sides of its pivotal axis, two operating arms, eachpivotally mounted. at one endand each resting at the other end on a different one of said rollers and each provided with a depending portionwhich cooper-. ateswith anadjustablev stop screw to limit therotation of the arm in one direction, the parts being so proportioned that said arms act through the medium of said rollers to bias said rotor to its intermediate position, two counterweight arms one pivotally attached intermediate its ends to each of said operating arms in such manner that each counterweight arm is free to rotate through a limited angle relative to the associated operating arm, and counterweights adjustably mounted on each. counterweight arm.

2.. A mechanism comprising a rotor movable between an intermediate and two efztreme positions, meansfor moving said rotor from its intermediate position to either extreme position, two rollers secured to said rotor on opposite sides of its pivotal. axis, two operating arms each pivotally mounted atone end and each resting at the other end. on adifferent one of said rollers and.

cash provided with a depending portion which cooperates. with, an. adjustablefstop screw, said stop screws being so adjusted that. when said rotor occupies its intermediate position the depending portion of, eacharm will engage the associated, stop screw but that when the rotor is rotated away from. its intermediate position in one direction the one arm will be raised and that when the rotor is rotated away from its intermediate position in the other direction the other arm will be raised, whereby the rotor is biased to its, intermediate position by said arms, two counterweight arms one pivotally attached intermediate its ends to each of said operating arms in such manner that each counterweight arm is free to rotate due to its. movements through a limited angle relative to the associated operating arm after the associated operating arm has been rotatedv by the rotor, and counterweights adjust ably mounted on each counterweight arm. I

3.,A mechanism comprising a rotor movable between an intermediate and two extreme positions, means for moving said rotor fromits intermediate position-to either extreme position, two rollers secured. tosaid rotor on opposite sides of its pivotalv axis, two operating arms each pivotally mounted at one end. and each resting at the other end. on. a different one of said'rollers and each provided. with. a depending; portion which cooperstop screw but that when the rotor is rotated away from its, intermediate position in one direction,

the one. arm will be raised and. that when the rotor is; rotated away fromits intermediate, p.osi,--

tion in theother direction the other arm. will: be. raised, whereby the-rotor is biased. to its intermediate position by said arms, counterweig-hts for assisting the arms in biasing the rotor to its intermediate position, a laterally projecting pin" secured to eachoperating arm, two pivoted rockers each: biased to one-position and each provided with an arm which cooperates with one of said pins in such. manner that the rocker assists in biasing the; rotor to its intermediate position and thatwhenthe associated arm is raised by rotation of the rotor it will rotate the rocker, and contacts operated by each rocker.

4. A mechanism comprising a magnetizable rotor movable between an intermediate and two extreme'positions, electromagnetic means cooperating with said rotor for moving said rotor from its intermediate position to either extreme posi tion, two rollers secured to said rotor on opposite sides of, its pivotal axistwo operating arms each pivotally mounted at one end and each resting at the other end on a different one of. said rollers and each provided with a depending portion which. cooperates with an adjustable stopscrew, said stop screws being so adjustedthat. when said rotor occupies its intermediate position the depending portion of. each armwill-engagetheaassociated stopscrew but that when the rotor is rotated away from its intermediate position in one direction the one arm will be raised and that when. the rotor is rotated away from itsintermediate position in the other direction the other arm will be raised, whereby the rotor. is biased to its intermediate position, by said arms, counterweights' for assisting the arms in biasing the rotor to its intermediate position, a laterally project,-

ingv pin secured to each operating arm, and contact mechanism operatively connected with each arm through the medium of the associatedpin: in

such manner that the contact mechanism isoperated'. when the associated operating arm is raised.

but that each operating arm is free to return to itsnormal position independently of the position of the contact mechanism.

A mechanism comprising a magnetizable rotor movablebetween an intermediate. and twov extreme positions, electromagnetic means: cooperating with said rotor for moving said rotor from its intermediate position. tov either extreme position, two rollers secured to said rotor'on opposite sides of its pivotal axis, two operating arms each pivotally mounted at one end and each resting at the other end on a different one of said. rollersland eachprovided with a depending portion which cooperates with anadjustable stop-screw, said stop screws being so adjusted that when said rotoroccupies its intermediate position the depending portion of each arm will engage the associated stop screw but that when the rotor is rotated away from its intermediate position in one direction the one arm'will be raised and that when the rotor is rotatedawayfrom its intermediate positionin the, other direction the other arm will be raised, whereby the rotor isbiasedto its intermediate positionby said arms,- counterweights for assisting the arms in biasing the rotor to its intermediate position, and contact mechanism operatively connected with each operating arm in such manner that the contact mechanism will become operated when the associated operating arm is raised but that each operating arm is free to return to the position to which it is biased by the associated counterweight without moving the contact mechanism.

6. A mechanism comprising a magnetizable rotor movable between an intermediate and two extreme positions, electromagnetic means cooperating with said rotor for moving said rotor from its intermediate position to either extreme position, two rollers secured to said rotor on oppo site sides of its pivotal axis, two operating arms each pivotally mounted at one end and each resting at the other end on a difierent one of said rollers and each provided with a depending portion which cooperates with an adjustable stop screw, said stop screws being so adjusted that when said rotor occupies its intermediate position the depending portion of each arm will engage the associated stop screw but that when the rotor is rotated away from its intermediate position in one direction the one arm will be raised and that when the rotor is rotated away from its intermediate position in the other direction the other arm will be raised, whereby the rotor is biased to its intermediate position by said arms, counterweights for assisting the arms in biasing the rotor to its intermediate position, and contact mechanism operatively connected with each operating arm in such manner that the contact mechanism assists in biasing the rotor to its normal position and that the contact mechanism associated with each arm will be operated when the associated arm is raised but that each operating arm is free to move to the position to which it is biased independently of the position of the associated contact mechanism.

7. A mechanism comprising a rotor movable between an intermediate and two extreme positions, means for moving said rotor from its intermediate position to either extreme position, two rollers secured to said rotor on opposite sides of its pivotal axis, two operating arms each pivotally mounted at one end and each resting at the other end on a different one of said rollers and each provided with a depending portion which cooperates with an adjustable stop screw to limit the rotation of the arm in one direction,

, the parts being so proportioned that said arms act through the medium of said rollers to bias said rotor to its intermediate position, two counterweight arms one pivotally attached intermediate its ends to each of said operating arms in such manner that each counterweight arm is free to rotate through a limited angle relative to the associatedoperating arm, counterweights adjustably mounted on each counterweight arm, a laterally projecting pin secured to each operating arm, two rockers pivotally mounted in a bracket and each biased to one position and each provided with a laterally projecting arm which cooperates with an associated one of said pins in such manner that each rocker will assist in biasing the rotor to its intermediate position and will be rotated in response to rotation of the associated operating arm when the associated operating arm is raised, a depending leg secured to each rocker, an adjustable stop screw cooperating with each leg to limit the rotation of the associated rocker, and contacts operated by each rocker.

8. A mechanism comprising a rotatable member, a weighted pivoted arm cooperating with said member to bias it to one position, motor means connected with said member for rotating it from said one position to another position in opposition to the bias of said arm, contact mechanism biased to one position and movable in opposition to its bias to another position, a pin secured to said Weighted arm, and another arm operatively connected with said contact mechanism and cooperating at its free end with said pin in such manner that said contact mechanism assists said weighted arm in biasing said rotatable member to its one position and that said contact mechanism will be operated to its other position by said pin in response to movement of said memher to its other position but that said pin is free to move out of engagement with said other arm in response to movement of said weighted arm in the direction to move said rotor to its one position, whereby if said contact mechanism sticks in its other position said weighted arm will continue to be effective to bias said rotatable member to its one position.

9. A mechanism comprising a rotatable memher, a weighted pivoted arm cooperating with said member to bias it to one position, motor means connected with said member for rotating it to said one position in opposition to the bias of said arm, a pivoted rocker biased by gravity to one position and movable to another position, contacts operated by said rocker, and single direction drive means connecting said rocker with said weighted arm and effective to move said rocker to its other position in response to movement of said rotatable member to its other position but ineffective to move said rocker in response to movement of said weighted arm in the direction to move said rotor to its one position,

10. A mechanism comprising a rotatable member movable between an intermediate and two extreme positions, motor means for moving said rotatable member from its intermediate position to either extreme position, two rollers secured to said rotatable member on opposite sides of its pivoted axis, two weighted operating arms pivotally mounted at one end and each resting at the other end on a different one of said rollers and together effective to bias said rotatable member to its intermediate position, two pivoted contact carrying rockers, and means for operatively connecting each rocker with a different one of said operating arms, each said means being so constructed and arranged that the associated rocker assists in biasing said member to its intermediate position and that the contacts carried by each rocker will be operated when the associated arm is moved in opposition to its bias but that in the event the contacts carried by either rocker stick in their operated positions the associated arm is free to move to the position to which it is biased independently of the position of the associated rocker.

WESLEY B. WELLS. WILLIAM K. LOCKHART. 

